Safety device for a syringe

ABSTRACT

The invention relates to a safety device ( 1 ) for a syringe ( 2 ), the device comprising a protective sheath ( 20 ) in which the syringe ( 2 ) can slide, said sheath ( 20 ) presenting an opening ( 36 ) at a distal portion ( 33 ), which opening is suitable for allowing the syringe ( 2 ) to project beyond the sheath ( 20 ). According to the invention, the sheath ( 20 ) presents radial resilience at its distal portion ( 33 ) suitable for enabling the sheath ( 20 ) to receive a cylinder ( 3, 19 ) of diameter greater than that of said opening ( 36 ).

The present invention relates to a safety device for a syringe, inparticular a prefilled syringe, enabling the needle thereof to beprotected after injection.

European patent application EP 0 966 983 discloses a safety system for aprefilled syringe, comprising a needle protection jacket engaged aroundthe syringe and situated inside a sheath, said jacket being suitable forsliding relative to the needle and to the sheath. At the end ofinjection, a spring causes the protective jacket to be expelled out fromthe sheath so that said jacket comes to cover the needle.

That system presents a certain number of drawbacks.

In order to expel the jacket, the user must exert relatively strongpressure on the head of the syringe piston in order to cause an abutmenton the jacket to go past an abutment on the sheath. In other words, theuser must perform an additional action following the action that givesrise to injection.

In addition, in the event of the user causing the jacket to be expelledwhile the syringe is still close to the patient, the jacket will strikethe skin of the patient and might injure the patient.

If the user moves the syringe further away prior to causing the jacketto be expelled, then the needle remains unprotected while the syringe isbeing taken further away, and that presents a risk of accidentalcontamination and/or injury.

French patent application FR 2 799 375 discloses an injector devicecomprising a syringe and a device for protecting the needle after use.That protection device comprises a locking ring having the syringe fixedtherein, with the resulting assembly being slidably engaged in aprotective case. At the end of injection, a spring causes theabove-mentioned assembly to move in such a manner that the needle iswithdrawn into the protective case.

That device presents relatively large size in the axial direction.

International patent application WO 00/33900 in the name of theApplicant company discloses a safety assembly for a prefilled syringecomprising a tubular sheath into which the syringe cylinder is inserteddirectly and is movable axially between an active, injection positionand a position for protecting the needle.

The present invention seeks to propose a safety device for a needle thatcan be actuated at the end of injection in a manner that is simple andthat does not require any additional action on the part of the user.

The present invention also seeks to provide a safety device which isadapted to at least two types of syringe, enabling syringes to be usedin a manner that is both convenient and safe, and that is alsoconvenient and inexpensive to make.

In a first aspect, the present invention thus provides a safety devicefor a syringe, in particular a prefilled syringe, the syringe comprisinga cylinder with a head at its proximal end, a needle carrier situated atthe distal end of the cylinder and provided with a needle, a pistonmounted to move in the cylinder, and a piston rod suitable for pushingthe piston, the device being characterized by the fact that it comprisesa sleeve suitable for receiving the syringe cylinder, the sleeve havinggrip means at its proximal portion for gripping the syringe head andsuitable for gripping syringes of at least two different types, and bythe fact that the device further comprises both a protective sheath inwhich the assembly constituted by the syringe and the sleeve can slidebetween a first position enabling injection to be performed and a secondposition in which the syringe needle is withdrawn inside the protectivesheath, and a resilient element acting between said sheath and saidassembly, enabling said assembly to be moved at the end of injectionfrom the first position into the second position by said assembly movingin reverse relative to the sheath.

The safety device of the invention is intended for single use and isadapted to standard syringes of the kind available on the market, whichare manufactured in large quantities and at relatively low cost.

In addition, because of its means for gripping the syringe head, thesafety device is adapted to a plurality of syringe types, thus enablinga user to have a single type of safety device for fitting to a pluralityof types of syringe, in particular 0.5 milliliter (mL) syringes and 1 mLsyringes.

The resilient element causes the syringe and the sleeve to moverearwards inside the protective sheath, and this is particularlyadvantageous insofar as the protective sheath does not run any risk ofstriking the skin of the patient and of injuring the patient, unlike thesystem described in above-cited European patent 0 966 983 in which theprotective jacket is expelled forwards.

The above-mentioned grip means are advantageously made at the proximalend of the sleeve, thus enabling the axial extent of the device to bekept small.

The grip means may comprise at least two elastically-deformable griptabs connected to a collar of the sleeve, the syringe head being grippedagainst said collar by the two tabs.

In a variant, the grip means comprise a collar connected by a pluralityof bridges of material to a top ring, the syringe head being retainedbetween the collar and the top ring.

The top ring may define an opening of axial section that is generallyfrustoconical, diverging upwards, thus making it easier to engage thesyringe head in said ring.

The protective sheath may include, in particular at its proximal end,elastically-deformable retaining tabs suitable for retaining theassembly constituted by the syringe and the sleeve in the first positionand suitable for being deformed so as to release said assembly, enablingit to slide axially relative to the sheath and to pass into the secondposition.

The retaining tabs may be moved apart in relatively simple mannerwithout requiring the user to exert a large force, the user not beingrequired to perform any additional action to actuate the safety deviceother than the conventional action of making an injection.

The retaining tabs may serve as abutments for the sleeve so that thesyringe secured to the sleeve is prevented from moving in translationrelative to the protective sheath when the user causes the needle topenetrate under the patient's skin.

The piston rod of the syringe may include a pushbutton arranged in sucha manner as to act directly on the retaining tabs.

This makes it possible to reduce the number of component parts in thesafety device, which can be of relatively low cost price.

In a variant, the device includes an unlocking element that is distinctfrom the syringe, and that is movable relative to the sheath andsuitable for acting on the retaining tabs.

Each of the above-mentioned grip tabs may include a surface againstwhich a retaining tab comes to bear.

In a variant, the retaining tabs come to bear on the collar of thesleeve.

The retaining tabs are preferably arranged in such a manner as to bemoved apart when they are actuated.

The above-mentioned unlocking element may include a button that isdistinct from the sleeve and that is fitted on the sheath.

In a variant, the button is made integrally with the sleeve, in whichcase the button may include a wall connecting it to the remainder of thesheath via a plurality of resilient arms.

Advantageously, the sheath includes a collar serving as a bearingsurface for the fingers of a user.

The sheath may include an inside wall that can be continuous, or that ispreferably discontinuous and against which the resilient element comesto bear.

In its distal portion, the sleeve may include studs suitable for cominginto contact into abutment against the above-mentioned bearing surfacewhen the device moves into its protective, second position at the end ofinjection.

In an embodiment of the invention, the sleeve comprises a solid-walledcylindrical tube.

This tube may be rigid and may include, preferably at its distal end, aplurality of the above-mentioned studs, preferably two studs.

The protective sheath may include a plurality, and preferably four,longitudinally-extending guide splines. These splines are disposed inpairs, and the splines in each pair are spaced apart by a predetermineddistance enabling a stud of the sleeve to engage between them.

In an embodiment of the invention, the splines are continuous, and oneof the splines in each pair comes to an end before the other spline soas to define a bottom passage enabling a stud of the sleeve to beinserted between the two splines by turning the sleeve relative to thesheath. For example, one of the splines may be shorter than the other.

In another embodiment of the invention, one of the splines in each pairis discontinuous and includes a passage enabling a stud of the sleeve tobe engaged therein and to be positioned between the two splines of thepair, and the sheath may include at least one portion in relief made onits inside wall and against which a stud comes into abutment while thesleeve is being inserted into the sheath, thus serving to position thestud in register with the above-mentioned passage.

The stud is inserted into the passage by turning the sleeve relative tothe sheath through a predetermined angle, e.g. through about one-fourthof a turn when the sheath has two pairs of splines.

After being turned in this way, the sleeve guided by the guide splinesis subjected to axial displacement inside the sheath until the retainingtabs are engaged on the grip means of the sleeve.

In another embodiment of the invention, the distal portion of the sleeveincludes longitudinal slots defining elastically-deformable tabs havingthe above-mentioned studs made thereon.

The device advantageously includes anti-return means that act when thesleeve and the syringe are in the second position to oppose saidassembly sliding out from the sheath, said means possibly comprisingelastically-deformable locking tabs made on the protective sheath, saidabove-mentioned studs of the sleeve being suitable for going past saidlocking tabs when the sleeve goes from the first position to the secondposition, and the locking tabs serving as abutments for the studs oncethe studs have gone past them.

The sheath and the sleeve may be made as respective single-piece parts.

The resilient element, e.g. a helical spring, may bear against a surfaceof the sleeve.

The protective sheath may be made of a material that is transparent orsemitransparent.

In a second aspect, the invention provides a safety device for asyringe, the device comprising a protective sheath in which the syringecan slide, said sheath presenting an opening at a distal portion, whichopening is suitable for allowing the syringe to project beyond thesheath, the device being characterized in that the sheath presentsradial resilience at its distal portion suitable for enabling the sheathto receive a cylinder of diameter greater than that of said opening.

By way of example, the cylinder is a cap for protecting the needle ofthe syringe. Under such conditions, the sheath serves to grip the capfirmly before the syringe is used, thus preventing any accident andprotecting the needle from contamination prior to injection.

The cylinder may also be the cylinder of the syringe, in particular whenthe syringe is about to be used. This ensures that the syringe isgripped firmly in the sheath, thus improving safety and accuracy ofinjection.

For a sheath that can be made by molding, the above-mentioned cylindermay also be constituted by a moving portion of the mold used for makingthe sheath. The radial resilience of the sheath makes it easy towithdraw the moving portion from the mold during unmolding.

In an embodiment, the distal portion of the sheath is frustoconical inshape.

In addition, the distal portion of the sheath may be split so as toimprove the radial resilience of the sheath. Thus, in an embodiment, thedistal portion of the sheath has a plurality of longitudinal slotsdefining converging resilient tongues.

The safety device may further include means for enabling the syringe toslide in the sheath between a first position enabling injection to beperformed and a second position in which the needle of the syringe iswithdrawn into the inside of the sheath.

In an embodiment, the safety device includes a sleeve suitable forreceiving the cylinder of the syringe, the sleeve having grip means atits proximal end for gripping the head of the syringe and suitable forgripping syringes of at least two different types, the assemblyconstituted by the syringe and the sleeve being capable of slidingbetween the first and second positions.

Preferably, the grip means are arranged to grip a collar forming thehead of the syringe.

There may also be provided a resilient element acting between the sheathand the assembly constituted by the sleeve and the syringe, and enablingsaid assembly to be caused to move, at the end of injection, from thefirst position into the second position by a rearward movement of saidassembly relative to the sheath.

The invention also provides an assembly comprising a syringe and asafety device as described above and fitted with said syringe.

The assembly may also include a cap protecting the needle of thesyringe. By way of example, said cap is mounted in such a manner as toproject beyond the sheath through the distal opening thereof.

Preferably, the sheath and the cap are arranged in such a manner as toact, after the cap has been removed, to prevent the cap from beingreinserted through the opening of the sheath.

The invention also provides a safety device for a syringe, the devicecomprising a protective sheath in which the syringe can slide, saidsheath presenting an opening at a distal portion, which opening issuitable for allowing the syringe to project beyond the sheath,characterized in that the sheath is radially deformable at its distalportion between a rest configuration in which its opening presents aminimum diameter, and a deformed configuration enabling a cylinder topass through the opening, said cylinder being of a diameter greater thanthe minimum diameter of the opening.

The invention will be better understood on reading the followingdetailed description of non-limiting embodiments, and on examining theaccompanying drawings, in which:

FIG. 1 is a diagrammatic and fragmentary view in axial section of asyringe fitted with a safety device in accordance with a firstembodiment of the invention, prior to injection;

FIG. 2 is a diagrammatic and fragmentary view in axial section on II-IIshowing the syringe and the device of FIG. 1;

FIG. 3 is a diagrammatic and fragmentary perspective view of theprotective sheath of the FIG. 1 device;

FIG. 4 is a diagrammatic and fragmentary view in perspective and inaxial section showing the FIG. 3 sheath;

FIG. 5 is a view analogous to that of FIG. 4 showing a sheath inaccordance with a variant embodiment of the invention;

FIG. 6 is a diagrammatic and fragmentary view in perspective of thesleeve of the FIG. 1 device;

FIG. 7 is a diagrammatic and fragmentary view in perspective of the FIG.1 syringe and device, prior to being assembled together;

FIG. 8 is a view analogous to that of FIG. 2, at the end of injection;

FIG. 9 is a view analogous to that of FIG. 2, after injection, theneedle being withdrawn into the protective sheath;

FIG. 10 is a view analogous to that of FIG. 2, the syringe havingdimensions that are different from those of the FIG. 2 syringe;

FIG. 11 is a diagrammatic and fragmentary view in axial section of asyringe fitted with a safety device in accordance with anotherembodiment of the invention, shown prior to injection;

FIG. 12 is a view analogous to that of FIG. 11, after injection, theneedle being withdrawn into the protective sheath;

FIG. 13 is a diagrammatic and fragmentary view in perspective of thesleeve of the FIG. 11 safety device;

FIG. 14 is a diagrammatic and fragmentary view in axial section of theFIG. 13 sleeve;

FIG. 15 is a diagrammatic and fragmentary view in axial section of asyringe fitted with a safety device in accordance with anotherembodiment of the invention;

FIG. 16 is a diagrammatic and fragmentary view in axial section of asyringe fitted with a safety device in accordance with anotherembodiment of the invention;

FIG. 17 is a diagrammatic and fragmentary axial section view of thesleeve of a device of the kind shown in the preceding figures, inaccordance with another embodiment;

FIG. 18 is a view analogous to FIG. 17, in a variant embodiment; and

FIG. 19 is a diagrammatic and fragmentary view in perspective and inaxial section of the FIG. 18 sleeve.

FIG. 1 shows a single-use safety device 1 in accordance with theinvention fitted to a prefilled syringe 2.

The capacity of the syringe 2 is 0.5 mL. It comprises a cylinder 3 ofaxis X fitted at its distal end with a needle carrier 4 having a needle5 mounted thereon. At its proximal end, the syringe cylinder 3 carries ahead or collar 6. This portion presents two parallel straight edges 6 a,as can be seen in FIG. 7. A piston 9 movable inside the cylinder of thesyringe serves to inject the substance contained therein, the piston 9being actuated by a piston rod 7 terminated by a pushbutton 8 on whichthe user exerts thrust in order to inject the substance.

In the description below, the terms “top” and “bottom” refer to theorientation selected for FIGS. 1 and 2 in which the needle 5 of thesyringe points towards the bottom of the page.

The needle 5 is initially protected by a cap 19 which the user removesprior to making an injection.

The safety device 1 comprises a sleeve 10 in which the cylinder 3 of thesyringe is engaged.

The sleeve 10, shown on its own in FIG. 6, is constituted over a majorfraction of its length by a cylindrical tube that is circularlysymmetrical about the axis X and that has a solid wall. At its proximalend, the sleeve 10 has a collar 11 and two elastically-deformable griptabs 12 that are diametrically opposite and that are connected to thecollar 11 substantially at its periphery.

These tabs 12 enable the syringe head 6 to be held on the collar 11.

At its top end, each tab 12 has a sloping flank 13 making it easy forthe syringe head 6 to go past the tabs 12 and snap-fasten therewith.

Behind each of the flanks 13, there is formed a notch 15 whose role isexplained below.

At its distal end, and on its outside wall, the sleeve 10 has twodiametrically opposite studs 16.

The diameter of the sleeve 10 and the dimensions of the tabs 12 areselected in such a manner as to enable the sleeve to receive two typesof syringe, e.g. syringes of the 0.5 mL type and syringes of the 1 mLtype, the device 1 fitted with a 1 mL syringe being shown in FIG. 10.

The sleeve 10 is for insertion into a protective sheath 20 shown inisolation in FIG. 3. At its proximal end, the protective sheath 20 has acollar 21 having a generally tubular top wall 22 connected thereto. Thecollar 21 serves as a bearing surface for the fingers of a userproceeding with an injection.

The tubular wall 22 has two windows 23, each presenting a top edge towhich a retaining tab 25 is connected. This tab is suitable for beingmoved away radially by elastic deformation.

The bottom portions of the windows 23 that are not occupied by theretaining tabs 25 leave a passage for the grip tabs 12 of the sleeve 10.

As can be seen in FIG. 2, when the sleeve 10 is in place in the sheath20, the retaining tabs 25 engage in respective notches 15 of the griptabs 12, thereby enabling the sleeve 10 to be retained in the sheath 20.

The pushbutton 8 is of a diameter that is sufficient to come intocontact with the retaining tabs 25 so as to move them apart at the endof injection.

On its inside wall, the protective sheath 20 has fourlongitudinally-extending guide splines disposed in pairs, the splines 26and 27 of a pair leaving between them a gap that enables the studs 16 ofthe sleeve 10 to engage between them.

The spline 27 is interrupted so as to form a passage 29. In registerwith the spline 27 there is formed an abutment 30 that is positionedrelative to the passage 29 in such a manner that when a stud comes tobear against the abutment 30, it is in register with the passage 29 andcan become engaged therein by turning the sleeve 10 relative to thesheath 20.

The sheath 20 also has two elastically-deformable locking tabs 31 madein its wall.

Each locking tab 31, situated between two splines 26 and 27 of a pair,includes an outwardly-directed curved end 32.

The curved ends 32 are situated above the abutments 30 so that when thesleeve 10 is being engaged in the sheath 20, the studs 16 do not need togo past the locking tabs 31.

In its distal portion 33, the protective sheath 20 is generallyfrustoconical in shape, converging downwards. This portion has fourslots 34 giving it a degree of radial resilience, thus enabling it toreceive the cap 19, or as explained below, another cylinder of diametergreater than that of the distal opening 36 of the sheath 20.

More precisely, the sheath 20 is radially deformable at its distal endbetween a rest configuration as shown in FIG. 9 where its opening 36presents a minimum diameter, and a deformed configuration as shown inparticular in FIG. 1, that allows a cylinder to pass through the opening36, said cylinder presenting a diameter that is greater than the minimumdiameter of the opening 36.

As described above, the cylinder may be the cap 19 for protecting theneedle 5 of the syringe 2, as shown in FIG. 1, from which it can be seenthat prior to injection the cap 19 is mounted in such a manner as toproject from the sheath 20 through the opening 36.

The sheath 20 thus clamps onto the cap 19, and exerts a force thereonthat opposes withdrawal of the cap, and that is sufficient to ensurethat the cap 19 does not become separated in untimely manner from thesyringe 2.

This reduces the danger of injury and contamination due to accidentalcontact of the needle 5 with a person other than the patient who is tobe injected.

In addition, as can be seen in FIG. 10, the sheath 20 and the cap 19 arearranged in such a manner as to prevent the cap 19 from being reinsertedinto the sheath 20 through its opening 26 after the cap 19 has beenwithdrawn.

Once the cap 19 has been withdrawn, the distal portion of the sheath 20contracts so that the opening 36 presents a diameter smaller than theoutside diameter of the cap 19. Specifically, the distal portion of thesheath clamps onto the syringe cylinder 3.

More precisely, although the opening 36 presents a rounded edge 38,beside its opening, the cap 19 presents a straight edge 39 which comesinto abutment against the rounded edge 38 of the opening 36.

Another cylinder suitable for being received in the sheath 20 throughthe opening may be constituted by the syringe cylinder 3 as shown inFIGS. 10 and 11 where, as explained below, there can be seen a syringe 2of size that is greater (in terms of diameter and length) than thesyringe 2 shown in FIGS. 1 and 2.

As can be seen in FIGS. 11 and 12, the syringe cylinder 3 is of a lengthsuch that while it is in its configuration prior to injection and duringinjection, it projects beyond the sheath 20 through the opening 36.

Because of the radial resilience of its distal portion 33, the sheath 20clamps onto the syringe cylinder 3, which in this case presents adiameter greater than the minimum diameter of the opening 36. Thisensures that the syringe cylinder 3 is held gripped close to the needlecarrier 4.

This grip, combined with the grip on the syringe head 6 provided by thesleeve 10, ensures that the syringe 2 is held rigidly within the sheath20, thus benefiting the safety and the accuracy of injection operations.

The sheath 20 may be made by molding. The mold used (not shown)comprises by way of example a stationary outer portion having a hollowwithin which there slides a substantially cylindrical moving portion,the mold cavity being formed between the stationary and moving portions.

Thus, another cylinder suitable for being received in the sheath 20through the opening 36 may be constituted by the moving portion of themold, which during unmolding, is withdrawn from the sheath 20 in theaxial direction through the opening 36. This withdrawal is made easierby the radial resilience of the distal portion 33 of the sheath 20.

As explained above, in order to make such radial resilience possible,the distal portion 33 of the sheath 20 is pierced by a plurality ofslots 34, in this case four slots, although some other number of slots(e.g. two or six) could also be envisaged.

These slots 34, which extend longitudinally and open out into theopening 36, define elastically flexible tongues 43 which convergedownwards and give the sheath 20 its radial resilience.

The sheath 20 also has two internal transverse shoulders 35 extendingbetween the guide splines 26 and 27 of a pair and situated above thecurved end 32 of the locking tabs 31.

The device 1 includes a helical spring 37 installed around the sleeve 10and bearing at one end against the shoulders 35 and at its other endagainst the collar 11.

The sleeve 10 is mounted in the sheath 20 as follows.

Initially, the sleeve 10 is positioned relative to the sheath 20 in sucha manner that the two grip tabs 12 are positioned between the tworetaining tabs 25 of the sheath 20.

The sleeve 10 is inserted into the sheath 20 while maintaining thisrelative position, with this initial insertion movement being continueduntil the studs 16 of the sleeve 10 come to bear against the abutments30 of the sheath 20.

As shown in FIG. 4, the sleeve 10 is then turned in the direction ofarrow F through one-fourth of a turn relative to the sheath 20, so as tocause each of the studs 16 to pass through a respective passage 29.

After turning in this way, the stud 16 is received between the splines26 and 27, and the sleeve 10 has a second insertion movement appliedthereto, urging it into the sheath 20. The studs 16 engaged between thesplines 26 and 27 then guide the sleeve 10 relative to the sheath 20.This movement is continued until the grip tabs 12 snap under theretaining tabs 25.

Once the sleeve 10 and the sheath 20 have been assembled together, theprefilled syringe 2 is inserted into the sleeve 10, with the syringehead 6 being positioned in such a manner that the straight sides 6 athereof face the grip tabs 12, as can be seen in FIG. 7.

The head 6 snap-fastens on the grip tabs 12 in such a manner as to beretained against the collar 11.

The studs 16 engaged between the splines 26 and 27 prevent the sleeve 10from turning relative to the sheath 20.

In the example described above, one of the splines is interrupted. In avariant, as shown in FIG. 5, all of the splines may be continuous, andone of the splines 26′ may terminate before the other spline 27′, sothat the spline 26′ is shorter than the other.

A bottom passage 29′ is thus provided beneath the spline 26′, enabling astud 16 of the sleeve 10 to be inserted between the two splines 26′ and27′ by turning the sleeve 10 through one-fourth of a turn in thedirection of arrow F′ relative to the sheath 20.

In this embodiment, only one axial insertion movement is requiredfollowed by a turning movement.

The operation of the safety device 1 is as follows.

To inject the substance contained in the syringe 2, the user appliesthrust to the pushbutton 8 so as to push in the piston 9.

At the end of the stroke of the piston 9 into the syringe cylinder 3,the pushbutton 8 causes the retaining tabs 25 to be moved apart so as torelease the sleeve 10, whereupon the spring 37 causes the assemblyconstituted by the sleeve 10 and the syringe 2 to move rearwards, as canbe seen in FIG. 8.

During this rearward movement, the studs 16 on the sleeve 10 go past thelocking tabs 31 of the sheath 20.

At the end of the stroke, as shown in FIG. 9, the studs 16 come intoabutment against the shoulders 35, and the needle 5 has been withdrawninto the sheath 20.

The studs 16 which are engaged above the curved ends 32 of the tabs 31prevent the sleeve 10 from moving towards the distal end of the sheath20.

This serves to lock the device 1 in its safe position, after injectionhas taken place.

FIGS. 11 to 14 show a safety device 40 constituting another embodimentof the invention.

This safety device 40 is arranged in such a manner as to receive astandard syringe 41 having 0.5 mL or 1 mL capacity, substantiallyanalogous to the above-described syringe 2.

The safety device 40 has a sleeve 42 in which the syringe cylinder 3 isengaged. As can be seen in particular in FIGS. 13 and 14, the proximalend of the sleeve 42 has means for gripping the collar or head 6 on thesyringe cylinder. These grip means comprise a collar 45 connected by aplurality of bridges of material 47, e.g. four bridges of material 47,to a top ring 46, the syringe head 6 being retained between the collar45 and said ring 46.

The ring 46 defines a top opening presenting in axial section a shapethat is generally frustoconical, diverging upwards, serving to guide thesyringe head 6 through said opening while the syringe is being mountedin the sleeve 42.

The sleeve 42 also has a shoulder 48 defining an enlargement in thesection of its proximal portion.

The sleeve 42 has a plurality of narrow, elastically-deformable tabs 51at its distal end, with the end of each tab carrying a stud 50.

After assembly, the syringe 2 and the sleeve 42 are prevented frommoving relative to each other.

The sleeve 42 is for engaging in a protective sheath 60 having a collar61 in its proximal portion with a bottom surface that serves as abearing surface for the fingers of a user during injection.

At its proximal end, the sheath 60 includes a plurality ofelastically-deformable retaining tabs 62 beneath the collar 61 which, atrest, are folded inwards.

Between the tabs 62 there are provided openings 63 having a role that isexplained below.

In the folded state, the retaining tabs 42 come to bear against thecollar 45 of the sleeve 42, thus limiting upward axial displacement ofthe assembly constituted by the sleeve 42 and the syringe 2.

Substantially halfway along its length in the example described, theprotective sheath 60 also includes a discontinuous internal bearingsurface 65. The end edge of the bearing surface 65 is generallyfrustoconical, diverging upwards, thus making it possible, duringinsertion of the sleeve 10 into the sheath 60, to guide the studs 50through said bearing surface 65.

The device 40 includes anti-return or locking means defined by lockingtabs 66 that are substantially analogous to the locking tabs 31described above, and that are made in the wall of the sheath 60.

The studs 50 can go past these locking tabs 66.

A helical spring 70 is placed in the sheath 60 around the sleeve 42bearing respectively against the bearing surface 65 and the shoulder 48.

The safety device 40 also has a button 71 including a cylindrical wall72 with hooks 73 at its distal end suitable for engaging in theabove-mentioned openings 63 in the sheath 60, situated between the tabs62.

At its proximal end, the cylindrical wall 72 presents an upwardlydiverging rim against which the user can apply a thumb in order todepress the pushbutton 71.

The distal edge of the button 71 is for coming into contact with thetabs 62 causing them to move apart.

The safety device 40 operates as follows.

The user inserts the needle 5 under the skin of the patient, with thesyringe being prevented from moving in translation relative to thesheath 60. In order to inject the content of the syringe, the userapplies the index and middle fingers against the collar 61 so as toenable the thumb to press against the head 8 with sufficient force toinject the substance.

At the end of the stroke of the piston rod 7 inside the cylinder 3, theuser makes use of the thumb which is pressed against the head 8 of thepiston to depress the button 71 without performing any additional actionother than that which gave rise to injection, thereby moving apart thetabs 62 and releasing the sleeve 42. The assembly constituted by thesyringe 2 and the sleeve 42 can then be driven upwards under drive fromthe spring 70.

During this upward displacement, the studs 50 go past the locking tabs66 and come into abutment against the bearing surface 65, thus limitingthe upward stroke of the assembly constituted by the syringe 2 and thesleeve 42, as can be seen in FIG. 12.

The needle 5 is then withdrawn inside the protective sheath 60 so it nolonger presents any danger of contamination and/or injury afterinjection.

Furthermore, the studs 50 engage above the tabs 66 prevent the sheathfrom being pushed out from the protective sheath 60, thus serving tolock the safety device 1, after use.

In the example described, the button 70 is constituted by a separateelement which is fixed on the protective sheath 60.

In a variant, and as shown in FIG. 15, the safety device includes abutton 71′ that is made integrally with the head 8 of the piston rod 7.This pushbutton 71′ has a concave surface 80 in its top portion enablingthe user to press a thumb thereagainst.

The button 71′ has a skirt 81 extending beneath the surface 80 andserving, when the piston rod 7 is substantially at the end of itsinjection stroke, to move apart the retaining tabs 62 and thus releasethe assembly constituted by the syringe 2 and the sleeve 42.

In another variant, as shown in FIG. 16, the safety device has a button71″. This button comprises a cylindrical wall 72″ which is connected tothe sleeve 42 via elastically-deformable arms 83.

In the example described, the cylindrical wall 72″, theelastically-deformable arms 83, and the sleeve 42 are made as a singlepiece.

At the end of injection, the pushbutton 71″ is pushed in and the wall72″ causes the tabs 62 to move apart so as to release the sleeve 42.

FIGS. 17 to 19 show two variant embodiments in which the shoulder 35 andthe curved end 32 both belong to the same resiliently deformable tab 32suitable for being pushed outwards, as represented in FIGS. 17 and 18 bydashed lines, under the effect of a radial force exerted outwards fromthe center of the sheath 20.

This feature makes it easier to insert the sleeve 10 during assembly ofthe device 1. By moving the tabs 31 outwards, the shoulders 35 are movedaway from the path of the studs 16, which have no difficulty in goingpast the tabs 31 so as to become positioned in the distal portion 35 ofthe sheath 20 (configuration shown in particular in FIG. 8).

As a result, there is no need to ensure that the sleeve 10 is in anyparticular orientation on being inserted into the sheath 20.

Conversely, after injection, the sleeve 10 reverses in the sheath, thestuds 16 going past the locking tabs 31 by moving them outwards untilthey become positioned, in the space left between the portions 32 andthe shoulders 35, as shown in FIGS. 17 and 18, the sleeve 10 then beingprevented from moving in the position it has thus reached, therebylocking the device 1 in its safe position.

This structural feature also simplifies fabrication of the sheath 20since there is no need to provide an outer mold in two parts with a joinplane extending between the shoulders 35 and the portions 32 of the tabs31.

Given the radial resilience of the tabs 31 including both the portions32 and the shoulders 35, the sheath 20 can be molded by means of twomold parts, a stationary outer part constituted by a single piece and aninner part that is movable in translation inside the outer part and thatcan be withdrawn towards the proximal end of the sheath 20 while movingapart the tabs 31 as it goes through.

As can be seen in FIGS. 17 to 19, the tabs 31 may be attached to a topportion of the sheath 20, situated beside its proximal portion (FIG.17), or to a bottom portion of the sheath 20, situated beside its distalportion 33 (FIGS. 18 and 19).

1. A safety device (1) for a syringe (2), the device comprising a protective sheath (20) in which the syringe (2) can slide, said sheath (20) presenting an opening (36) at a distal portion (33), which opening is suitable for allowing the syringe (2) to project beyond the sheath (20), the device being characterized in that the sheath (20) presents radial resilience at its distal portion (33) suitable for enabling the sheath (20) to receive a cylinder (3, 19) of diameter greater than that of said opening (36).
 2. A device according to claim 1, characterized in that said cylinder (19) is a cap for protecting the needle (5) of the syringe (2).
 3. A device according to claim 1, characterized in that said cylinder (3) is the cylinder of the syringe (2).
 4. A device according to claim 1, characterized in that the sheath is made by molding, and said cylinder is a moving portion of a mold.
 5. A device according to claim 1, characterized in that the shape of the distal portion (33) of the sheath (20) is frustoconical.
 6. A device according to claim 1, characterized in that the distal portion (33) of the sheath (20) is split.
 7. A device according to claim 6, characterized in that the distal portion (33) of the sheath (20) has a plurality of longitudinal slots (34) defining converging resilient tongues (43).
 8. A device according to claim 1, characterized in that it includes means for enabling the syringe (2) to slide in the sheath (20) between a first position enabling injection to be performed and a second position in which the needle (5) of the syringe (2) is withdrawn into the inside of the sheath (20).
 9. A device according to claim 8, characterized in that it includes a sleeve (10) suitable for receiving the cylinder (3) of the syringe (2), the sleeve (10) having grip means at its proximal end for gripping the head (6) of the syringe (2) and suitable for gripping syringes of at least two different types, the assembly constituted by the syringe (2) and the sleeve (10) being capable of sliding between the first and second positions.
 10. A device according to claim 9, characterized in that the grip means are arranged to grip a collar (6) forming the head of the syringe (2).
 11. A device according to claim 9, characterized in that it includes a resilient element (37) acting between the sheath (20) and the assembly constituted by the sleeve (10) and the syringe (2), and enabling said assembly to be caused to move, at the end of injection, from the first position into the second position by a rearward movement of said assembly relative to the sheath (20).
 12. An assembly comprising a syringe (2) and a safety device (1) fitted to said syringe (2), the assembly being characterized in that said safety device (1) is in accordance with claim
 1. 13. An assembly according to claim 12, characterized in that it further includes a cap (19) protecting the needle (5) of the syringe (2).
 14. An assembly according to claim 13, characterized in that said cap (19) is mounted in such a manner as to project beyond the sheath (20) through the distal opening (36) thereof.
 15. An assembly according to claim 14, characterized in that the sheath (20) and the cap (19) are arranged in such a manner as to act, after the cap (19) has been removed, to prevent the cap from being reinserted through the opening (36) of the sheath (20).
 16. A safety device (1) for a syringe (2), the device comprising a protective sheath (20) in which the syringe (2) can slide, said sheath (20) presenting an opening (36) at a distal portion (33), which opening is suitable for allowing the syringe (2) to project beyond the sheath (20), characterized in that the sheath (20) is radially deformable at its distal portion (33) between a rest configuration in which its opening (36) presents a minimum diameter, and a deformed configuration enabling a cylinder (3, 19) to pass through the opening (36), said cylinder being of a diameter greater than the minimum diameter of the opening (36). 